Sifting device and method for filtering with the aid of said sifting device



Aug. 22, 1961 G. DE GOOIJER 2,997,179

SIFTING DEVICE AND METHOD FOR FILTERING WITH THE AID OF SAID SIFTINGDEVICE Filea July 28, 1959 2 Sheets-Sheet l 619th? De (30037690 BY; VW

ATTOR/VEYS g- 1951 G. DE GOOIJER 2,997,179

SIFTING DEVICE AND METHOD FOR FILTERING WITH THE AID 0F SAID SIFTINGDEVICE Filed July 28, 1959 2 Sheets-Sheet 2 INVENTOR.

ATTOR NEYS United States Patent 2,997,179 SIFTING DEVICE AND METHOD FORFILTERING WITH THE AID 0F SAID SIFTING DEVICE Gerrit de Gooijer, 7AOverstraat, Amerongen, Netherlands Filed July 28, 1959, Ser. No. 830,011Claims priority, application Netherlands July 28, 1958 3 Claims. (Cl.210-400) The invention relates to a sifting device for sucking 01f aliquid from a suspension on a continuously running belt and a method forfiltering a suspension, whereby on the surface of the belt liquid isremoved from said suspension With the aid of a decreased pressure on theother side of the belt.

Sifting devices provided with an endless sifting belt and also providedwith a fixed suction box having a suction mouthpiece over which theendless sifting belt moves forward, are known.

A device of this sort has the drawback that the mouthpiece of thesuction box and the sifting belt are subjected to heavy wear and tearbecause of the friction existing between said parts. This disadvantageincreases in proportion to the effectiveness of the suction device andthe degree of vacuum.

This is generally the case when a low pressure in the suction box isdesirable. In this case the mouthpiece of the suction box should fitclosely against the sifting belt so that a tightness against thepenetration of false air is obtained.

In addition to this, a further drawback also occurs in that the siftingbelt is held back and is deformed by the vacuum in the suction box.

It is known, in order to lessen the wear of the suction box in siftingdevices of the above-named type, to have said sifting devices providedwith a perforated endless cloth running round the suction box, which isarranged between the mouthpiece of the suction box and the belt carryingthe width of material, whereby the endless cloth is on both sides of theperforated part provided with compact rims which have backs running inlongitudinal direction, that grip into corresponding grooves of the siderims of the mouthpiece of the suction box, in such a way that atightness against the penetration of false air is obtained. In thiscase, however, the wear and tear which used to be caused by the frictionof the sifting belt over the mouthpiece of the suction box, is nowcaused by the backs running in longitudinal direction that grip intocorresponding grooves of the side rims of the mouthpiece.

It is, therefore, an object of the invention to construct a siftingdevice which practically does not show any wear by friction betweensifting belt or filtering belt and suction box mouthpiece.

A further object of the invention is a 'very effective sifting devicewith a high vacuum in the suction box and in which the packing againstthe penetration of false air between the rim of the mouthpiece of thesuction box and the belt can be effected in a simple and adequate way.

Another object of the invention is a sifting device with a flatfiltering belt which is sucked off evenly over the whole of its breadth.

A still further object of the invention is a sifting. device with a fiatfiltering belt with extremely small apertures.

And yet another object of the invention is a tobacco leaf which is madewith the sifting device according to the invention.

The sifting device according to the invention eliminates the wear andtear of the sifting belt and the mouthpiece by applying a movablesuction box with mouthpiece, which suction box intermittently followsthe movement 2,997,179 Patented Aug. 22, 1961 of the belt from astarting position, and after this returns to said starting position, andwith a vacuum apparatus also operating intermittently and synchronouslyto the movement of the suction box, which vacuum apparatus sucks the boxwhile it is following the belt.

Preferably the device according to the present invention is alsoprovided with a support for the sifting belt, which during suctionbrings the sifting belt into or keeps it in the desired form and whichis positioned in the mouthpiece of the suction box, while a packing canbe fastened on the rim of the mouthpiece of the suction box against thepenetration of air.

Hereby it becomes possible to maintain a high vacuum in the suction boxduring suction, such as is desirable for instance in producing -asynthetic tobacco leaf, whereby a suspension, containing 1 part byweight of ground tobaccoz20 to 50 parts by weight of liquid, preferably1 part by weight of ground tobaocoz40 parts by weight of liquid, are tobe filtered on an endless filtering belt with the aid of a siftingdevice.

An abnormal wear of the sifting belt and the suction box is preventedbecause in this invention sifting belt and suction box do not make anymovements relative to one another during suction.

It is now possible to provide the mouthpiece of the suction box withtightly fitting packing material, preferably by soft rubber or the like.

In one embodiment the sifting device is provided with a driven eccentrichaving a driving-shaft mechanism, controlling the suction pump acting asa suction device as Well as the movement of the suction box with themouthpiece and in which a spring, which is provided about the drivingshaft belonging to the box, presses the mouthpiece of the suction boxagainst the filtering or sifting belt during the time that the boxfollows the movement of the belt, while the box, after attaining theend-position of this movement, leaves the filtering belt and returns toits starting position on a semi-circular way.

In this way a very simple synchronous coupling between the suctiondevice and the movement of the suction box is obtained, while in thatcase the eccentric can be coupled to the driving mechanism of the beltin a simple way, for instance by a string.

If care is taken that the length of the movement of the box with thebelt and the length of the mouthpiece of the box are chosen in such away, that the mouthpiece in the starting position of the box partlyoverlaps the reach of the belt which had been sucked ofl when the boxwith the belt were in the end-position of the preceding movement, theWhole of the belt will be sucked off without any places being left onthe belt which are not sucked off.

In another embodiment the suction box repeatedly executes a forward andbackward movement over rails running parallel to the upper part of thebelt, whereby a suction device, more specially a suction pump,periodically sucks the belt against the box, causing the box to becarried along with the belt, executes the forward movement and tightensa draw spring, and whereby the belt loosens itself from the box at theend of said suction period, the draw spring sets the box back to thestarting position.

In this embodiment the movement of the suction box is automaticallysynchronized with the movement of the belt, in that the belt carries thesuction box along with it as long as there is sufiicient vacuum in thebox. If care is taken that the movement of the box and the belt duringthe suction stroke is less than the length of the box mouthpiece andthat in addition the back-stroke period of the pump is sufficientlyshort, the belt can be completely sucked off without a coupling, forinstance a mechanical or electrical one, being present between thedriving mechanism for the belt and the one for the suction device.

Hereby it is possible to choose the length of the mouthpiece withrespect to the displacement of the belt in such a way, that thedisplacement of the mouthpiece makes out a fraction only of the lengthof the mouthpiece, which makes it possible for the belt to be locallysucked off by a plurality of suction strokes.

It is also possible to position several boxes one behind the other underthe upper part of the belt and, if desired, to provide these with aseparate suction mechanism.

Each box will then be able to suck off a fixed reach of the belt, andthis in such a way that the belt is sucked off completely.

In this case it is no longer necessary for the mouthpiece of the box tooverlap a reach of the belt which had been sucked off during a precedingmovement.

The invention will now be further illustrated with the aid of a drawingin which a couple of embodiments are shown.

FIGS. 1 and 2 show schematical front and side views of a sifting deviceaccording to the invention, in which the suction box repeatedly carriesout a movement which is such that the box during part of this movementpresses against the sifting belt or filtering belt and follows the belt,while simultaneously to this part of the movement or the box a vacuumapparatus operating synchronously with the movement, sucks the box,after which the box leaves the belt and returns to the starting positionon a semicircular Way.

FIGS. 3 and 4 represent schematical top and side views of a siftingdevice according to the invention in which the suction box executes abackwards and forwards movement in such a way, that the suction boxlocally follows the filtering belt by the belt being sucked against thebox, and a spring restores the box to the starting position after theunder-pressure in the box has fallen away.

FIG. 5 shows another embodiment of a vacuum apparatus operatingsynchronously with the movement of the box.

In the FIGURES 1 and 2, 1 is an endless sifting belt or filtering beltwith a movable suction box 2 arranged underneath.

The movable suction box 2 is by means of a rod system 3, 4 connected toan arm 5' which is driven by a pulley 6.

A centre of rotation 8 is provided with a sliding bearing 7 in which therod 4 can move backwards and forwards.

The suction box 2 is also provided with a centre of rotation 9 with asliding bearing 10 for the rod 4.

The rod 4 is further provided with a stop 11. Now when the centre ofrotation 12 of arm 5 executes a revolution, the rotation centre 13, thepoint of junction of the rods 3 and 4, executes a circular movementround the rotation centre 8.

In consequence of this movement the suction box 2 also carries out acircular movement round the centre 8.

Hereby the slack spring 14 takes care, that the suction box 2 is movedalong the rod 4 in such a way, that the suction box is pressed againstthe belt, in that part of its circular movement in which it follows thebelt. Of course the pulley 6 should be driven in such a way, that thesuction box, in that part of its movement, in which it follows the belt,travels at practically the same speed as does the belt. The pulley 6also drives an arm 15 which is provided with a rotation centre 16. Apiston pump 17 is fastened to the rotation centre 16 by means of a rodsystem 13, 19.

A flexible lead 20 connects the pump 17 with the suction box 2 and isprovided with a ball valve 21, which opens itself at the moment in whichthe pump starts its suction stroke, that is at the moment or just afterthe moment that the suction box begins to follow the belt.

The ball valve 21 shuts itself at the beginning of the back stroke ofthe pump that is at the moment or just before the moment at which thesuction box leaves the belt.

The pump is further provided with a ball valve 22.

The liquid sucked off with the solid particles therein, if any, whichhave passed through the belt are sluiced out through this valve duringthe back stroke of the pump.

In FIGS. 3 and 4, 1 is an endless sifting belt; in FIG. 3 the siftingbelt or filtering belt 1 has for the sake of clarity only been indicatedby a dash-dot line.

The suction box 2 is positioned on the guiding rods 25 and 26 with thesliding bearings 23.

The draw spring 27 is connected on the one side to the suction box 2 andon the other side to a fixed point of the device.

If the suction lead connection 28 is connected for instance to amembrane pump by means of a suction lead, the belt is sucked against thesuction box at the location of the box during the suction stroke of thepump and the box is carried away with the belt, causing the draw springto be tightened, while at the return stroke of the pump the belt loosesitself from the box and the box, which is now free from the belt, is setback to the starting position by the draw spring.

The supports 29 are provided in the mouthpiece 30 of the suction box forthe purpose of locally bringing and/ or maintaining the belt in thedesired form during sucking oiI.

The mouthpiece 30 of the suction box serves to tighten the suction boxduring the suction stroke of the pump. As a matter of course themouthpiece 30 can again be provided with a tightly fitting packingmaterial.

In FIG. 5 the suction lead 20, which connects the suction box 2 with thevacuum buffer vessel 35, is interrupted by a three-way valve 33.

A pressure regulator 36, for instance in the form of a contactmanometer, controls the motor of the vacuum pump 37 in such a way, thata sufficient vacuum is always retained in the vessel 35.

When the spring 27 returns the suction box to the starting position ofits movement the stop 31-mechanically or electricallysets the valve 33to that position at which the passage between the buffer vessel 35 andthe suction box 2 is open.

The belt 1 now carries the suction box 2 with it until the stop 32 hasbeen reached.

The stop 32 now turns the valve in such a way that the latter closes thepassage between the buffer vessel 35 and the suction box 2 and at thesame time connects the suction box 2 to the outer air by means of thelead 34-, causing the box to loose itself from the belt. The liquidsucked off from the suspension should be drained regularly from thebuffer vessel 35. The apparatus necessary for this purpose is notindicated in the schematical drawing.

It is evident that a vacuum apparatus of this description can also beapplied in a device as represented in the FIGURES l and 2.

In these figures the arm 15, the rotation centre 16, the piston pump 17and the rod system 18, 19 can as a matter of course be left out.

I claim:

1. A sifting device which comprises an endless sifting belt continuouslymoving over at least two spaced parallel horizontal rollers, at leastone suction box having a mouthpiece applicable to form a seal with thesaid sifting belt, a vacuum means which sucks the sifting box and thebelt against each other causing said box to be carried forward with thesifting belt, a means to release the vacuum in said box after said boxhas travelled a predetermined distance with said belt and a draw springattachec" to said suction box which is tensioned by the forward movementof said box, and which restores the suctior box to its starting positionupon release of the vacuum.

References Cited in the file of this patent UNITED STATES PATENTS DixonSept. 27, Consuegra et al. Feb. 2, Wallny L Mar. 24, Thompson Sept. 18,Komline July 121,

